During the signal integrity analysis work based on schematic only, I meet
a concept word of "Manhanttan Length". ProtelDXP assumes that this is the
length of the real board track. Who can tell me the meaning of this word?

In the district of Manhattan, New York City, you can only travel along the
streets, you can't just go from point A to point B.

The direct distance from point A to point B we call "as the crow flies."
That's the straight line, and it would be the length of a track if there
were one track from point A to point B.

The "Manhattan Length" of a route between two points is the distance that
the tracks would total if they run only in the x or y directions. So if we
have two points, A(X1, Y1) and B(X2, Y2), the Manhattan distance between
the two points is the sum of the absolute values of (X2-X1) and (Y2-Y1).